Add sync error logging, extend error flash, fix unload saves

- Log workforce sync errors to backend stdout so they appear in docker logs
- Extend error flash from 5s to 15s so errors are readable
- Replace sendBeacon (POST-only) with keepalive fetch (PUT) on unload —
  sendBeacon was hitting 404s on all three unload saves

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/node_modules/own-keys/test/index.js

@@ -0,0 +1,72 @@
+'use strict';
+
+var test = require('tape');
+var hasSymbols = require('has-symbols/shams')();
+var hasPropertyDescriptors = require('has-property-descriptors')();
+
+var ownKeys = require('../');
+
+/** @type {(a: PropertyKey, b: PropertyKey) => number} */
+function comparator(a, b) {
+	if (typeof a === 'string' && typeof b === 'string') {
+		return a.localeCompare(b);
+	}
+	if (typeof a === 'number' && typeof b === 'number') {
+		return a - b;
+	}
+	return typeof a === 'symbol' ? 1 : -1;
+}
+
+test('ownKeys', function (t) {
+	t.equal(typeof ownKeys, 'function', 'is a function');
+	t.equal(
+		ownKeys.length,
+		1,
+		'has a length of 1'
+	);
+
+	t.test('basics', function (st) {
+		var obj = { a: 1, b: 2 };
+		if (hasPropertyDescriptors) {
+			Object.defineProperty(obj, 'c', {
+				configurable: true,
+				enumerable: false,
+				writable: true,
+				value: 3
+			});
+		}
+
+		st.deepEqual(
+			ownKeys(obj).sort(comparator),
+			(hasPropertyDescriptors ? ['a', 'b', 'c'] : ['a', 'b']).sort(comparator),
+			'includes non-enumerable properties'
+		);
+
+		st.end();
+	});
+
+	t.test('symbols', { skip: !hasSymbols }, function (st) {
+		/** @type {Record<PropertyKey, unknown>} */
+		var obj = { a: 1 };
+		var sym = Symbol('b');
+		obj[sym] = 2;
+
+		var nonEnumSym = Symbol('c');
+		Object.defineProperty(obj, nonEnumSym, {
+			configurable: true,
+			enumerable: false,
+			writable: true,
+			value: 3
+		});
+
+		st.deepEqual(
+			ownKeys(obj).sort(comparator),
+			['a', sym, nonEnumSym].sort(comparator),
+			'works with symbols, both enum and non-enum'
+		);
+
+		st.end();
+	});
+
+	t.end();
+});